Like the almighty pop trinity of Britney, Justin, and Christina before her, Hilary Duff has made the leap from the Disney Channel to MTV. The 15-year-old’s faux-rock single ”Why Not” — one of two songs she recorded for the platinum-selling ”Lizzie McGuire Movie” soundtrack — was a ”TRL” smash. Now, with her Lizzie McGuire persona abandoned for good, the budding princess of all media is preparing to release her first all-original, full-length album, ”Metamorphosis,” on Aug. 26. The effervescent Duff, who’s also filming her next movie, a romantic comedy called ”A Cinderella Story,” tells EW.com about her musical tastes and her multitasking life — and tells Michelle Branch to stop hating.

What got you started with music? About two years ago I saw my [18-year-old] sister, Haylie, with her band. They were rehearsing and dancing and it looked so much fun. And I told my mom that I wanted to be involved in singing also, and she was like, ”All right!” So I started taking classes, and next thing I knew I was in the studio.

How is it different from acting for you?The thing I liked about singing is most people know me as characters I played before, like Lizzie McGuire. But singing is really personal. It’s a good way to get everyone to know more about Hilary.

A lot of your stuff has a rock feeling to it. How’d that happen? I definitely didn’t want, like, a really poppy album, because that’s not what I listen to. I wanted to do music that I really like, and that I would actually listen to. It is pop music but it has some more rock and edginess to it.

What DO you listen to? Man, I listen to everything. I listen to a lot of eclectic kind of music, ’cause my mom and my sister really influence it a lot. I like the Eagles, I like Bob Dylan, I like Janis Joplin, and I also like 50 Cent and Black Eyed Peas and Justin Timberlake and Britney Spears and Vanessa Carlton.

I guess she said that it was one of the worst songs she’d heard recently.That’s funny. I’ve always respected Michelle Branch and I like her music. I think it’s really mean and it makes everybody look ugly to hate on people and to say mean things. But if she didn’t like my song that’s fine. You can’t make everybody happy.

Maybe she didn’t mean it…I’m sure she did, if she said it!

Your new single, ”So Yesterday,” feels more grown-up than ”Why Not” — what attracted you to it?It’s funny because I heard it for the first time and I was like, ”I don’t really like this song.” I started listening to it more and more and I kind of started to like it. And I was like, ”OK, I’m going to go in the studio and give this 100 percent and I’m not gonna say anything bad about it.” And I ended up loving it. It was such a fun song, and it means a lot. It’s very empowering toward breaking up with your boyfriend and getting over it and stuff.

Do you want to be as big as Britney?Britney Spears… that sounds so huge! She’s awesome, I love her so much. And I think it’s been really hard for her — like all the things you see her go through in the press and stuff. But I would love for my albums to be as successful as hers have been.

How are you able to fit in your music stuff with the movie you’re filming?I’m working on the movie but also I have music rehearsals every night, just to get ready for shows with my band. I’m doing both at the same time. It’s fun. I’m 15 so I have lots of energy and I’m not tired yet!